The invention relates to a method and an arrangement for checking the authenticity of a first communication subscriber in a communications network.
In a communications network, data is generally transmitted between communication subscribers, for example a service provider and a service user. In order to protect a communications network against penetration of an unauthorized communication subscriber into the communications network, the authenticity of each communication subscriber is generally checked.
3G TS 33.102 Version 3.0.0 Draft Standard, 3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, 3G Security, Security Architecture, 05/1999 (“the 3G reference”) discloses a method and an arrangement for checking the authenticity of a communication subscriber, in particular of a service provider or of a service user in a communications network.
The method known from the 3G reference and the corresponding arrangement are based on what is referred to as 3G TS 33.102 Version 3.0.0 Draft Standard, which describes a security architecture of a mobile phone system.
In FIG. 4, the procedure during the checking of the authenticity of a communication subscriber, such as is known from the 3G reference is illustrated symbolically and parts thereof will be explained below briefly.
A transmission of data is illustrated in FIG. 4 by an arrow in each case. A direction of an arrow characterizes a transmission direction during a data transmission.
FIG. 4 shows a mobile phone system 400, comprising a user 401 of a communication service, for example a mobile phone, and a provider 402 of a communication service. The provider 402 comprises a dial-in network 403 with a dial-in network operator from which the user 401 locally requests a communication service, and a home network 404 with a home network operator with which the user 401 is signed on and registered.
In addition, the user 401, the dial-in network 403 and the home network 404 each have a central processing unit with a memory, for example a server (central computing unit), with which processing unit the procedure described below is monitored and controlled and on which memory data is stored.
The dial-in network 403 and the home network 404 are connected to one another via a data line over which digital data can be transmitted. The user 401 and the dial-in network 403 are connected to one another via any desired transmission medium for the transmission of digital data.
During a communication, the user 401 dials 410 into the dial-in network 403. At the start of the communication, checking of both the authenticity of the user 401 and the authenticity of the provider 402 is carried out.
To do this, the dial-in network 403 requests 411 what is referred to as authentication data from the home network 404, with which data the authenticity of the user 401 and of the provider 402 can be checked.
The authentication data which is obtained from the home network 404 comprises a random number and a sequential number of the provider 402. The sequential number of the provider 402 is obtained in such a way that a counter of the provider 402 increases the sequential number of the provider 402 by the value 1 at each attempt at communication between the user 401 and the provider 402.
It is to be noted that the random number and the sequential number of the provider 402 only constitute part of the authentication data and are not to be understood as comprehensive. Further authentication data is known from the 3G reference.
The home network 404 transmits 412 the requested authentication data to the dial-in network 403. The dial-in network 403 processes the received authentication data in a suitable way 413, and transmits the processed authentication data to the user 401.
The user 401 checks 415 the authenticity of the provider 402 using a dedicated sequential number, which is handled in a way corresponding to the sequential number of the provider 402, and using the sequential number of the provider 402.
The procedure during the checking of the authenticity of the provider 402 is described in the 3G reference.
A result of the checking of the authenticity of provider 402, “authenticity of provider satisfactory” 416, “authenticity of provider satisfactory but sequential fault has occurred” 417 or “authenticity of provider not satisfactory” 418, is transmitted 419 from the user 401 to the provider 402.
In the case of the result “authenticity of provider satisfactory” 416, the dial-in network 403 checks 420 the authenticity of the user 401 as described in the 3G reference.
In the case of the result “authenticity of provider not satisfactory” 418, the communication is interrupted and/or restarted 421.
In the case of the result “authenticity of provider satisfactory but a sequential fault has occurred” 417, resynchronization takes place in such a way that the home network 404 transmits 422 a resynchronization request to the user 401. The user responds with a resynchronization response in which resynchronization data is transmitted 423 to the home network 404. The sequential number of the provider 402 is changed 424 as a function of the resynchronization response. The authenticity of the user 401 is then checked, as is known from the 3G reference.
The procedure described has the disadvantage that during checking of the authenticity of a communication subscriber, in particular during the checking of the authenticity of a service provider, a large amount of data has to be transmitted between the communication subscribers.